A technique is known, wherein provisional collision positions are predicted on the basis of an orbit of a subject vehicle and an orbit of a moving object to count a number of times of determination of the provisional collision position for each of the provisional collision positions, and the position, which has the largest number of times of determination of the provisional collision position, is predicted as the collision position of the moving object in relation to the subject vehicle (see, for example, Patent Document 1).
In the case of this technique, it is possible to predict the collision position. However, it is impossible to enhance the judgment accuracy for whether or not the subject vehicle and the moving object collide with each other and the judgment accuracy for whether or not the moving object exists. That is, the radius of curvature of the subject vehicle is estimated on the basis of a detected steering angle, while the detection accuracy of a radar is not enhanced. Therefore, it is impossible to enhance the detection accuracies as described above.